1. Field of Invention
This invention relates to blends of polybenzimidazole polymers with polyarylate polymers. More particularly this invention relates to membranes produced from the blend of polybenzimidazole polymers and polyarylate polymers.
2. Prior Art
Polybenzimidazoles are a known class of heterocylic polymers which are characterized by a high degree of thermal and chemical stability. Processes for their production are disclosed in U.S. Pat. No. Re. 26,065, and U.S. Pat. Nos. 3,313,783, 3,509,108, 3,555,389, 3,433,772, 3,408,336, 3,549,603, 3,708,439, 4,154,919 and 4,312,976 (all patents are herein incorporated by reference). Polybenzimidazole polymers have been formed into membranes, ultrafilters, reverse osmosis devices and other types of separatory media of great utility.
While membranes and other products produced from polybenzimidazole polymers can be employed in electrodialysis, reverse osmosis and for a wide range of other separatory uses, the pore size of many polybenzimidazole products is quite small, i.e., less than about one angstrom. Thus, polybenzimidazole products are generally not useful as filter for molecules having molecular weights greater than about 1,000. In addition, the use of polybenzimidazole products is frequently impractical because of their relatively high cost.
Polyarylates are high temperature, high performance thermoplastic polymers with a good combination of thermal and mechanical properties. They also have good processability which allows them to be molded into a variety of useful articles. However, the utility of the polyarylates is severely limited in the aerospace industry, where resistance to paint strippers such as methylene chloride is required. Though generally resistant to chemical reaction, they are degraded when exposed to chlorinated solvents, ethylene glycol, N,N-dimethyl formamide and inorganic acids, such as hydrochloric acid, among others.
Polyarylates have frequently been blended with other types of materials to offset a defect in one material with a favorable characteristic of another material. For example, a material having a low heat distortion temperature but possessing other valuable characteristics, may be blended with a material having a high heat distortion temperature to improve the overall heat distortion characteristics of the blend.
U.S. Pat. No. 4,259,458 discloses polyarylates that have been blended with polyesters and at least one thermoplastic polymer selected from the group consisting of an aromatic polycarbonate, a styrene resin, an alkyl arylate resin, a polyurethane, a vinyl chloride polymer, a copolyetherester block polymer or a polyhydroxyether.
In addition, polyarylates blended with polyetherimides are disclosed in U.S. Pat. No. 4,250,279. Blends of polyarylates with polycarbonates have also been disclosed, for example, in U.S. Pat. Nos. 3,792,115, 3,864,428, 4,180,494, 4,189,579, 4,259,458, 4,264,487, 4,273,899, 4,286,075, 4,324,869 and 4,369,136.
U.S. Pat. No. 4,113,683 discloses the production of high temperature resistant polymer compositions capable of use in the formation of fiber reinforced composite articles. These articles are prepared from partially plasticized organic fibers derived from polymers comprised of a nitrogenous intractable, high temperature resistant polymer, such as a poly (bisbenzimidazobenzophenantholine), and related nitrogenous polymers, such as polybenzimidazoles, polyamides and high temperature aromatic polyesters. Onto these fibers is affixed a composition solution consisting of a nitrogenous intractable high temperature resistant polymer and an admixture comprising a major amount of the nitrogenous intractable, high temperature polymer previously discussed, and a minor amount of a crosslinkable polymer exhibiting a glass transition temperature of above 200.degree. C. While this patent arguably discloses the use of a polybenzimidazole and a polyester as components of a polymer composition, it fails to disclose the specific mixture of a polybenzimidazole polymer with an aromatic polyester to form the product disclosed in this invention or the process for the production of that product.
Accordingly it is an object of the present invention to prepare polybenzimidazole/polyarylate blends.
It is a further object of this invention to prepare polybenzimidazole/polyarylate blends which are formed into membranes.
It is a further object of this invention to prepare membranes from a blend of a polybenzimidazole with a polyarylate which can separate a broad range of molecular weight compounds.
It is an additional object of this invention to prepare membranes from a blend of a polybenzimidazole with a polyarylate which membranes exhibit good ion exchange properties, microporous structure and high regeneration efficiency.
These and other objects, as well as the scope, nature, and utilization of the process and product will be apparent from the following description and appended claims.